Metabolomic Analysis of Flavour Development in Mung Bean Foods: Impact of Thermal Processing and Storage on Precursor and Volatile Compounds

Consumers prefer mung beans for their low allergenicity and nutritional benefits. However, flavour development in mung bean foods has been problematic, with beany flavour being a limiting factor. Hot processing is crucial in forming mung bean flavours, and storage-induced changes in flavour precursors directly impact the taste post-processing. This study used metabolomics to analyse the effects of hot processing (baking and cooking) on mung bean flavour and differences after storage. A total of 131 flavour precursors and 45 volatile substances were identified across six sample groups. The results showed that baking and cooking upregulated 22 and 18 volatile substances (ketones, aldehydes, esters, pyridine, pyrazines, etc.), respectively. The Maillard reaction during baking notably increased compounds like 2-hydroxypyridine, 2-methoxy-3-isobutyl pyrazine, 1,2-hexanedione, and 2,3-butanedione. Both methods inhibited linoleic acid oxidation, significantly reducing hexanal content, a key "bean" odour substance. However, storage accelerated linoleic acid conversion to C13 peroxides, increasing hexanal content and bean odour. This process decreased precursor substances like glucose-1-phosphate and caused the accumulation of pyruvic acid intermediates in pentose phosphate and pyruvate metabolism/amino acid metabolism pathways, leading to reduced mung bean taste richness.